System and method for liquid air production, power storage and power release

ABSTRACT

Systems and methods for storing and releasing energy comprising directing inlet air into a vertical cold flue assembly having an air inlet at or near its top into which inlet air is directed and an exit at or near its bottom. The air is cooled within the cold flue assembly and a portion of moisture is removed from the air within the cold flue assembly. The air is directed out the exit of the cold flue assembly and compressed. The remaining moisture is substantially removed and the carbon dioxide is removed from the air by adsorption. The air is cooled in a main heat exchanger such that it is substantially liquefied using refrigerant loop air, the refrigerant loop air generated by a refrigerant loop process. The substantially liquefied air is directed to a storage apparatus. The refrigerant loop air is cooled by a mechanical chiller and by a plurality of refrigerant loop air expanders. In energy release mode, working loop air warms the released liquid air such that the released liquid air is substantially vaporized, and the released liquid air cools the working loop air such that the working loop air is substantially liquefied. A portion of the released liquid air is directed to the at least one generator and used as bearing air for the at least one generator. The substantially vaporized air is directed to a combustion chamber and combusted with a fuel stream. Combustion gas may be directed from the combustion chamber to at least one expander and expanded in the expander, the expanded combustion gas split into a first portion and a second portion, the first portion being relatively larger than the second portion. The first portion may be directed to a first heat exchanger, and the second portion may be directed to a second heat exchanger such that the second portion heats and substantially vaporizes the released liquid air.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/406,754, filed on Mar. 18, 2009, which is incorporated herein byreference in its entirety and which is a continuation-in-part of U.S.patent application Ser. No. 12/127,520, filed on May 27, 2008, which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to power storage and release systems andmethods.

BACKGROUND OF THE INVENTION

Wind power is desirable because it is renewable and typically cleanerthan fossil fuel power sources. Wind turbines capture and convert theenergy of moving air to electric power. However, they do sounpredictably and often during low power demand periods when the valueof electric power is substantially lower than during peak demandperiods. Without a way to achieve certainty of delivery during peakdemand periods (also known as “firm” power), and without a way to storelow-value off-peak power for release during high-value peak periods, thegrowth of wind power and other intermittent renewable power sources maybe constrained, keeping it from reaching its full potential as part ofthe world's overall power generation portfolio.

Another disadvantage of intermittent power sources such as wind is thatthey can cause system “balance” problems if allowed onto thetransmission grid, which is a major hurdle for new (particularlyrenewable) power generation sources to clear. Operating wind turbines(or other intermittent renewable power assets) adjacent to and inconjunction with a natural gas—(NG) fired turbine can yield 100%certainty of power, because the NG turbine can “back up” the wind.However, that approach will yield a reduced environmental rating, basedon the hours of operation for the NG turbine and may be economicallyunfeasible because the two power output systems need to be fullyredundant, and thus capacity utilization and economic return-on-assetsis diminished. Most importantly, neither a standard wind farm nor aback-up NG turbine(s) can “store” the wind power that may be widelyavailable during the off-peak periods.

A disadvantage of other types of utility-scale power sources is thatthey produce large and unnecessary amounts of power during off-peakperiods or intermittently. Another major disadvantage of existing powersystems, both firm and intermittent, is that transmission lines oftenbecome “clogged” or overloaded, and transmission systems can becomeunbalanced. One existing solution for overloaded transmission lines istransferring power by “wheeling,” which is the delivery of a specificquantity of power to each end-user, allowing any “power product” toenter the power transmission system and be used to “balance” any otherproduct that was removed from the system. A disadvantage of usingcurrent storage systems for wheeling is that power production occursduring all hours (most of which are not peak demand hours), and does notsubstantially overlap with peak demand hours. Another disadvantage isthat transmission of power, which occurs at all hours (most of which arenot peak demand hours), also does not substantially overlap with peakdemand hours.

The few utility-scale power storage systems that exist today (or havebeen proposed previously) also have major disadvantages such asinefficient heat and cold recovery mechanisms, particularly those thatrequire multiple systems for hot and cold storage media. Anotherdisadvantage is extra complexity in the form of many expanders andcompressors often on the same shaft with “clutches” that allow somefront-end elements to be disconnected from the back-end elements on thesame shaft. Some existing power plants use a simple cycle gas turbinewith a recuperator, where a front-end compressor is on the same shaft asthe hot-gas expander that compresses the inlet air. However, in thatconfiguration some 63% of the power output is devoted to compressinginlet air.

Therefore, there exists a need for a system that can provide certaintyand a firm, consistent energy output from any power source, particularlyintermittent power sources such as wind. There is also a need to providea convenient storage system for power that can be used in connectionwith power generation sources that generate large amounts of powerduring off-peak periods, including both firm (i.e., baseload) andintermittent power sources. There is a further need for a power storageand release assembly having more efficient hot and cold recoverymechanisms and simpler, more efficient, compression and expansionsystems.

SUMMARY OF THE INVENTION

The present invention, in its many embodiments, alleviates to a greatextent the disadvantages of known power storage systems by convertingenergy to liquid air (L-Air) for power storage and release and using theL-Air and ambient air for heat exchange purposes. All of the cold fromreleased L-Air is recovered by a working loop of air for greater energyoutput. Embodiments of the present invention provide energy efficientstorage, replacement and release capabilities by cooling and warming airthrough heat exchange, recovering both heat and cold from the system,storing energy as liquid air and pumping liquid air to pressure torelease energy.

Embodiments of the present invention may be referred to herein asVandor's Power Storage (VPS) Cycle. The VPS Cycle includes systems andmethods of storing power and systems and methods of energy release. Anembodiment of the VPS Cycle's method of storing power comprisesdirecting inlet air through a vertical cold flue assembly having an airinlet at or near its top into which the inlet air is directed and anexit point at or near its bottom. The inlet air sinks downward from thetop of the cold flue assembly to the bottom of the cold flue assembly.The storage method further includes the steps of cooling the air withinthe cold flue assembly and removing a portion of the moisture from theair within the cold flue assembly. The cold flue assembly includes aninsulated aluminum plate fin heat exchanger configured to operate in avertical manner (with the plates in an optimum, such as concentriccircle, arrangement) so that the entire assembly resembles (in ahorizontal cross sectional or plan view) a round “flue.” Although use ofthe cold flue assembly is preferred, an ordinary plate fin heatexchanger in a horizontal configuration could be used in the powerstorage methods.

The air is directed out the exit of the cold flue assembly. Then the airis compressed and the heat of compression recovered from the compressedair. Preferably, compression of the air includes two-stages ofcompression where the air is first compressed to a first pressure atthis stage of the cycle and the heat of compression recovered from thecompressed air. The recovered heat of compression from the compressedair may be directed to an absorption chiller to drive the absorptionchiller. The absorption chiller is fluidly connected to the cold flueassembly. Refrigerant may be directed from the absorption chiller to thecold flue assembly to help cool the inlet air entering the cold flueassembly. The remaining moisture and carbon dioxide (CO₂) are removedfrom the air by adsorption, preferably using a molecular sieve assembly.

Next, in a preferred embodiment, the air is compressed to a secondpressure and the heat of compression is again recovered from thecompressed air. It should be noted that the compression could beperformed in a single stage with some loss of efficiency or in three ormore stages with efficiency gains but increased complexity and capitalcosts. A preferred embodiment of the storage method next comprisescooling the air in a main heat exchanger such that the air issubstantially liquefied using refrigerant loop air, the refrigerant loopair generated by a refrigerant loop process. Finally the substantiallyliquefied air is directed to a storage apparatus, preferably a liquidair storage tank.

A vapor portion of the substantially liquefied air in the storageapparatus, or “flash air” may be directed to the main heat exchanger,and recovered cold from the vapor portion used to further cool the inletair flowing in. This vapor portion would thus be warmed by the inletair. The vapor portion is further warmed, preferably to approximately220° F. and specifically by the heat of compression recovered fromelsewhere in the process. The warmed vapor portion of the substantiallyliquefied air is directed to the molecular sieve assembly so that thesubstantially liquefied air removes the carbon dioxide and moisture thathad been collected there. The warm sweep air, which is still at nearlythe 70 psia pressure at which it left the storage tank as flash air,moves on to a generator-loaded hot-gas expander, producing power that isused on-site to run some of the instruments, valves, pumps and othersuch devices, and thus improving the relationship between the totalamount of power delivered for storage to the system and the amount ofL-Air that results from that power. (This is called “sweeping” themolecular sieve assembly; thus, the warmed vapor portion of thesubstantially liquefied air directed to the molecular sieve assembly isalso referred to as “sweep air” herein.).

The storage method also preferably comprises compressing a refrigerantloop air stream to a first pressure, while recovering the heat ofcompression, then compressing the refrigerant loop air to a second andoptionally a third pressure and again recovering the heat ofcompression. The refrigerant loop air is then split so that a firstportion is directed to a mechanical chiller and a second portion isdirected to a refrigerant loop air cryogenic expander. The refrigerantloop air is then cooled in the mechanical chiller and the refrigerantloop air cryogenic expander and directed back to the main heatexchanger, where it is further cooled and then expanded to further coolthe stream. The refrigerant loop air then is returned to the main heatexchanger as the deeply cooled refrigerant stream that cools the inletair to be liquefied. Refrigerant may be directed from the absorptionchiller to the mechanical chiller to cool the mechanical chiller.Returning to the refrigeration cycle, the refrigerant air stream iswarmed by the inlet air and is returned to the beginning of the loopwhere it is recompressed and chilled again, as outlined above.

An embodiment of an energy storage system comprises one or more inletair compressors. A single multi-stage compressor or a plurality ofcompressors may be used to compress the inlet air that is to beliquefied and stored, depending on the desired configuration. The systemmay also comprise a molecular sieve assembly fluidly connected to afirst inlet air compressor. In a preferred embodiment, a vertical coldflue assembly is fluidly connected to the molecular sieve assembly andto a second inlet air compressor and has an air inlet at or near its topinto which the inlet air is directed and an exit at or near its bottom.The cold flue assembly preferably consists of a plate fin heat exchangerand has an air inlet at or near its top into which the inlet air isdirected and an exit at or near its bottom.

An absorption chiller using working fluid is fluidly connected to thecold flue assembly. The energy storage system also comprises one or moreheat exchangers including a main heat exchanger, preferably a cryogenicheat exchanger, fluidly connected to at least one of the one or moreinlet air compressors. The assembly further comprises a storageapparatus fluidly connected to the main heat exchanger. A mechanicalchiller containing refrigerant fluid is fluidly connected to theabsorption chiller, and a refrigerant loop air assembly is fluidlyconnected to the mechanical chiller.

In a preferred embodiment, the refrigerant loop air assembly comprisesone or more refrigerant loop air compressors and one or more refrigerantloop air cryogenic expanders, with at least one of the compressors beingfluidly connected to the main heat exchanger. The mechanical chiller isfluidly connected to at least one refrigerant loop air compressor, to atleast one refrigerant loop air expander, to the absorption chiller andto the main heat exchanger. In this embodiment, the refrigerant loop airflows from the refrigerant loop air assembly to the main heat exchangerto cool and liquefy the inlet air.

In a preferred embodiment of the refrigerant loop process, the airstream flows through a connected loop from an independent refrigerationassembly comprising a plurality of refrigerant loop air compressorswhich compress the refrigerant loop air such that the refrigerant loopair is compressed to a first pressure and the heat of compression isrecovered. The refrigerant loop air is compressed to a second pressureand the heat of compression is recovered. The refrigerant loop air issplit such that a first portion is directed to the mechanical chillerand a second portion is directed to at least one refrigerant loop aircryogenic expander. The refrigerant loop air is cooled by the mechanicalchiller and by the one or more refrigerant loop air cryogenic expanders.The refrigerant within the mechanical chiller is condensed by coldworking fluid sent to the mechanical chiller from the absorptionchiller.

An embodiment of an energy release system comprises a storage apparatusand one or more heat exchangers wherein at least one of the heatexchangers is fluidly connected to the storage apparatus. At least onecombustion chamber is fluidly connected to at least one of the heatexchangers. One or more generator-loaded hot-gas expanders are fluidlyconnected to the at least one combustion chamber and to at least one ofthe heat exchangers. The system further comprises at least one generatorfluidly connected to at least one of the expanders, the generatorproducing electric power. In an embodiment of the energy release system,liquid air is released from the storage apparatus and flows in a firstgeneral direction. Working loop air flows in a second general direction,and the second general direction is substantially opposite to the firstgeneral direction. The working loop air warms the released liquid airsuch that the released liquid air is substantially vaporized, and thereleased liquid air cools the working loop air such that the workingloop air is substantially liquefied. The two streams never mix, but onlyexchange heat energy in one or more heat exchangers. The substantiallyliquefied working loop air is then pumped to pressure and vaporized byhot combustion gas. The vaporized high pressure working loop air isexpanded in a generator-loaded hot-gas expander, wherein the generatorproduces electric power.

A portion of the released liquid air is directed to the at least onegenerator and used as bearing air for the generator. The substantiallyvaporized air is directed to a combustion chamber and combusted with afuel stream. Combustion gas is directed from the combustion chamber toat least one expander and is expanded in the expander. The expandedcombustion gas is split into a first portion and a second portionwherein the first portion is relatively larger than the second portion.The first portion of the combustion gas is directed to a first heatexchanger, where it vaporized the released and previouslypumped-to-pressure liquid air, and the second portion is directed to asecond heat exchanger such that the second portion heats andsubstantially vaporizes the liquid air that is produced in the loop airsegment of the power outflow cycle. In this manner, the heat energycontained in the hot exhaust gas that exits a generator-loaded expanderis used first to vaporize and warm the inlet air to the combustionchamber, and secondly to vaporize and warm the liquid air produced inthe loop air portion of the cycle, allowing that hot, high pressure airstream to also be expanded in its own generator-loaded expander. Thusthe cold energy contained in the outward flowing, pumped-to-pressureL-Air is used to liquefy a smaller stream of loop air, and the hotenergy contained in the expanded combustion gas is used to vaporizethose two pumped to pressure liquid air streams, both producing power.

Embodiments of the present invention include methods of releasing storedenergy comprising releasing stored liquid air, pumping the releasedliquid air to pressure, and directing the released liquid air through atleast one heat exchanger in a first general direction. Working loop airis directed through the at least one heat exchanger such that theworking loop air flows in a second general direction wherein the secondgeneral direction is substantially opposite to the first generaldirection. The released liquid air is warmed by the working loop airsuch that the released liquid air is substantially vaporized, and theworking loop air is cooled by the released liquid air such that theworking loop air is substantially liquefied. The substantially liquefiedworking loop air is then pumped to pressure and vaporized by heatexchange with hot combustion gas. The pressurized working loop air isthen expanded in a generator-loaded hot-gas expander such that thegenerator produces electric power.

Methods of releasing stored energy further comprise directing a portionof the released liquid air to at least one generator and using thereleased liquid air as bearing air for the generator. The releasedliquid air cools the generator, and the generator warms the releasedliquid air. In a preferred method, a plurality of heat exchangers isprovided and at least one of the heat exchangers is a cryogenic heatexchanger. An embodiment of the release method further includesdirecting the substantially vaporized and pressurized air to acombustion chamber and combusting the substantially vaporized air with afuel stream. Combustion gas is directed from the combustion chamber to afirst generator-loaded hot-gas expander, and the combustion gas isexpanded in the first generator-loaded hot-gas expander.

The expanded combustion gas is then split into a first portion and asecond portion with the first portion being relatively larger than thesecond portion. The first portion is directed to a main heat exchanger,where it vaporizes the main outflow stream of pumped-to-pressure liquidair and the second portion is directed to a second heat exchanger suchthat the second portion heats and substantially vaporizes the liquid airin the loop that is used to recover the cold from the main released air,where the loop air is heated and expanded in a second generator-loadedhot-gas expander. The formerly hot exhaust stream is directed from themain heat exchanger to a moisture separator, and the moisture from thehot exhaust stream is recovered in the moisture separator. Thatrecovered liquid moisture is then pumped to pressure, warmed byrecovered heat in a heat exchanger, and the recovered moisture isdirected to the first generator-loaded hot-gas expander.

Thus, embodiments of the present invention provide energy storagemethods and systems and energy release methods and systems to providefirm, consistent power from wind energy or other energy sources. Theseand other features and advantages of the present invention will beappreciated from review of the following detailed description of theinvention, along with the accompanying figures in which like referencenumerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects of the invention will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a process diagram of an embodiment of a power storage methodand system in accordance with the present invention; and

FIG. 2 is a process diagram of an energy release method and system inaccordance with the present invention.

DETAILED DESCRIPTION

In the following paragraphs, embodiments of the present invention willbe described in detail by way of example with reference to theaccompanying drawings, which are not drawn to scale, and the illustratedcomponents are not necessarily drawn proportionately to one another.Throughout this description, the embodiments and examples shown shouldbe considered as exemplars, rather than as limitations on the presentinvention. As used herein, the “present invention” refers to any one ofthe embodiments of the invention described herein, and any equivalents.Furthermore, reference to various aspects of the invention throughoutthis document does not mean that all claimed embodiments or methods mustinclude the referenced aspects. Reference to temperature, pressure,density and other parameters should be considered as representative andillustrative of the capabilities of embodiments of the invention, andembodiments can operate with a wide variety of such parameters.

Referring to FIG. 1, an embodiment of a method and system for storingpower is shown. The power storage system 20 generally comprisescompression, cooling and clean up system 22 and independentrefrigeration system 24, with both systems fluidly connected via mainheat exchanger 100, which is preferably a cryogenic heat exchanger. Coldflue assembly 7 is vertically oriented with a top and a bottom andincludes a plate fin heat exchanger (not shown). The vertical plate finheat exchanger preferably has concentric “nested” circular plates (notshown). In some embodiments, the plates are like barrels within barrels,with a manifold at the top and bottom to hold them in place. The platespreferably are separated by fins. The manifolds allow the various fluidstreams to enter and exit the top, middle and bottom of cold flueassembly 7. The cold flue assembly 7 may include a protective cover (notshown) and an air filter 23 at the top, and a set of condensation plateswithin the “flue”. Those condensation plates allow the moisture contentof the falling and cooling air to condense at approximately 32° F.,removing approximately 90% of the moisture content of the air, allowingthe cold water to be circulated to the top of the cold flue to act as arefrigerant to pre-cool the incoming (warm) air, after which it is sentto a drain or to the cooling tower that serves the absorption chiller 8,and which should be deemed to be “within” the rectangular symbol 8 shownon FIG. 1.

Instead of a normal flue that efficiently allows hot gases to rise tothe top of the flue by “stack effect”, the “cold flue” design allows thechilled air to sink through the top of the cold flue assembly, where itenters the flue at atmospheric pressure (approximately 14.7 psia) andwarm temperatures (e.g., as warm as about 95° F.), laden with as much asabout 55% relative humidity, and continues falling by gravity as it ischilled in the cold flue, sinking through the plate fin heat exchanger,increasing its density as it falls deeper into the flue, and reachingthe bottom, sinking through the bottom and passing into an aircompressor through the inlet to the compressor flange at sub-zerodegrees (F.) temperature, with very little pressure drop, without theneed for electric powered blowers and fans to move it along. It shouldbe noted that an ordinary plate fin heat exchanger in a standardhorizontal configuration could be used instead of the cold flueassembly.

In a preferred embodiment, absorption chiller 8 is fluidly connected tocold flue assembly 7 at two locations so refrigerant may be directed tothe cold flue assembly to cool the air that enters it, cycle through andthen return to the absorption chiller to be re-cooled. Cooling isprovided by refrigerant stream 66, preferably cold aqueous ammonia,which, after removing the heat from the falling air, is sent back to anabsorption chiller for re-cooling. The colder the inflow air, the denserit is, and the less energy input will be required to compress it. It isthat increasing density that, by gravity, allows the air to fall downthe cold flue 7 toward the first compression, with very little pressuredrop. The absorption chiller is “powered” by several heat recoverysystems (heat exchangers) where the heat of compression is the heatsource used by the absorption chiller. For the sake of clarity, thoseheat exchange loops are not shown. Instead, those sources of heat energyfor the absorption chiller are shown as the various inter- andafter-coolers at each compressor. The one exception is intercooler 700which delivers its heat of compression mostly to sweep air stream 545which is thus warmed and used to “sweep” or regenerate molecular sieve10, purging its CO₂ and moisture content. Prior to venting that sweepair stream through vent 19, the sweep air is expanded to just nearlyatmospheric pressure in hot-gas expander 345 which is loaded bygenerator 630, thus producing power that can be used by various pumps,sensors, meters and motors. The expansion of the warm sweep air 545 ispossible because the flash air that is the source of the sweep air leftthe cryogenic storage vessel at a pressure of approximately 70 psia. Theflash-to-sweep air route not only serves to recover the cold energy ofthe flash air, in heat exchanger 100, but also serves to recover theheat of compression found in inter-cooler 700, thus allowing that hotsweep air to produce “free” power in generator loaded expander assembly34, 3, 630.

In this context, the term “inlet air compressors” used in the summary ofthe present invention refers to those compressors shown on FIG. 1 thatbring the ambient inlet air up to pressure prior to liquefaction andarrival in the liquid air storage tank. Those inlet air compressors areshown as 200 and 210 on FIG. 1, but may be configured in various otherways. A first compressor 200 is directly below and fluidly connected tocold flue assembly 7. Compressor 200 is in fluid connection with firstinter-cooler 700, which may provide waste heat to warm flash stream 535and warm vapor portion 545, as described above. The cooling and clean upsystem 22 of energy storage system 20 further comprises molecular sieveassembly 10, which could be a multi-vessel configuration, a pre-coolingheat exchanger 110 and a second compressor 210 and after-cooler 710.After-cooler 710 is fluidly connected to the main heat exchanger 100,which is in fluid connection with one or more of compressors 200 and 210and storage apparatus 16, a cryogenic, insulated tank suitable forstoring liquid air.

The storage method will now be described. Inlet air 500 is directedthrough vertical cold flue assembly 7. The inlet air 500 enters the top26 of the cold flue assembly, preferably from at least one power source1 (which could be any firm, i.e., base load, power source or anyintermittent power source such as a wind turbine). Cold flue assembly 7includes a plate fin heat exchanger (not shown). The inlet air 500 sinksdownward through the plate fin heat exchanger and through the bottom 28of the cold flue assembly 7. The “cold flue” design allows the chilledinlet air 500 to fall from the top, where it enters the flue andcontinues falling by gravity as it is chilled in the cold flue,increasing its density as it falls deeper into the flue, and reachingthe inlet to the compressor flange at approximately 32° F., with verylittle pressure drop, without the need for electric powered blowers andfans to move it along. Refrigerant stream 66 cools the inlet air 500 asit passes through cold flue assembly 7. Thus, the inlet air 500 iscooled and moisture is removed from the air within the cold flueassembly 7.

The inlet air 500 (likely warm in the summer and cold in the winter)sinks to the bottom of cold flue assembly 7 and, as partially cooled air510, enters the first compressor 200, or first stage of a multi-stagecompressor, where it is compressed to a first pressure of approximately35 psia. The power to drive the compression steps and cooling steps ofthe method is provided by power sources or energy conversion sources,which include, but are not limited to, wind power when such power isavailable, power from an electric grid or an independent power plant,nuclear, coal, geothermal, solar, hydropower, landfill gas, anaerobicdigester gas, coal bed methane, associated gas, recovered heat fromlarge industrial plants, recovered cold from liquid natural gas importterminals, wave and tidal energy.

The heat of compression preferably is recovered and directed toabsorption chiller 8 to drive the absorption chiller. In a preferredembodiment the heat of compression is used to warm the sweep air 545that regenerates a molecular sieve, as described above and below.Another use for the recovered heat of compression is to provide (heat)energy to an absorption chiller whose purpose is described below. Thepartially cooled inlet air 510, having given up approximately 90% of itsmoisture content continues to molecular sieve assembly 10 where its CO₂content and the remaining moisture are removed from the air byadsorption in zeolyte or other such materials known in the art. In apreferred embodiment, that moisture is regenerated (or purged of itssaturated CO₂ and moisture) by warm, medium-pressure air that begins as“flash” air in the L-Air storage tank and serves as the “sweep air” 545that regenerates the molecular sieve. Such molecular sieve arrangements,utilizing two or more vessels, and relying on a hot, clean, pressurizedgas for regeneration, are commonly used in various gas processingsystems and are well understood by process designers and manufacturers.The molecular sieve assembly 10 may be a multi-vessel configuration,allowing for regeneration of one or more vessels while one or more ofthe remaining vessels remove the CO₂ and moisture from the air stream.The remaining moisture and carbon dioxide (CO₂) are removed from the airby adsorption, preferably using a molecular sieve assembly.

Exiting the molecular sieve assembly 10, the dry inlet air 520 isfurther cooled by the absorption chiller and compressed to a secondpressure of approximately 75 psia and after the removal and recovery ofthe heat of compression, as described above, moves on toward the mainheat exchanger 100 at approximately 50° F. It should be noted that asingle stage of compression of the air could work, but would likelyyield reduced efficiency. Alternatively, three or more stages ofcompression could work and may yield better efficiencies but with addedcomplexity and increased capital costs. As discussed below, the selectedexit pressure from the second stage of compression (or single stage ifperformed with one compression stage) may vary and will depend on theselected storage temperature and pressure for the liquid air that isstored in storage tank 16.

The cool (but not cold), dry, approximately 74 psia inlet air 520, witha very low CO₂ content of approximately 1.0 parts per million, thenenters the main heat exchanger 100 for cooling. The dry inlet air 520 ischilled to approximately −283° F., and having lost some pressure, exitsthe main heat exchanger 100 as substantially liquefied (and partially asa cold vapor) air 530 at approximately 73 psia, travels throughcryogenic flow and pressure control valve 400 and enters a storageapparatus 16, preferably an insulated, cryogenic, L-Air storage tank(s)at approximately 70 psia and about −283° F. 75 psia was selected in thismodel so as to allow the liquid air that is produced by the in-flowcycle to be stored at that pressure in an L-Air storage tank, at about−283° F. Other storage pressures will yield other temperatures for theL-Air, and may be selected, in lieu of the about 70 psia, −283° F.conditions discussed here. In that event, the compression toapproximately 75 psia in the second stage would be adjustedappropriately. Those decisions are “optimizations” that may be selectedas part of the engineering process for each deployment. Anotheroptimization might use three-stages of inlet air compression.

Approximately 15% of the inflowing substantially liquefied air 530 will“flash” as the liquid plus vapor enters the storage tank atapproximately −283° F. and about 70 psia. While this vapor portion 535,or flash air, is quite cold, it is a relatively small stream. Therefore,this cooling of the partially cooled inlet air 510, to substantiallyliquefied air 530, is performed by a refrigerant air stream. Independentrefrigeration system 24 provides the bulk of the refrigeration requiredto liquefy the dry inlet air 520. In a preferred embodiment, independentrefrigeration system 24 may include a cryogenic aircompression/expansion refrigeration system augmented by a mechanicalchiller 30, which is augmented by the ammonia absorption chiller 8.

The independent refrigeration system, or “refrigerant loop airassembly”, comprises a continuous loop of air (refrigerant loop air540), which is independent of the inflow air that is sent to the liquidair storage tank. That refrigerant loop comprises several compressors(shown as 220, 230 and 240 on FIG. 1, which may be referred to as“refrigerant loop air compressors) and several cryogenic expanders(shown as 300 and 310 on FIG. 1, which may be referred to as“refrigerant loop air cryogenic expanders”), where the expansion ofhigher-pressure air causes that air (the working fluid) to be chilled.The chilling of that air stream is augmented moderately by a standardmechanical chiller, which in turn is aided by the low-grade cooling froman absorption chiller. The absorption chiller gets its energy fromrecovered heat of compression, and assists the mechanical chiller byhelping to condense the refrigerant (working fluid) within themechanical chiller. The configuration shown on FIG. 1 indicates thatcompressor 220 is fluidly connected to the main heat exchanger, and thatexpander 310 is so connected. However, other configurations are coveredby embodiments of the invention and may be selected for reasons relatedto capital cost relative to operating efficiencies or other reasons.

Mechanical chillers typically contain an evaporator, compressor andcondenser and are driven by an electric motor or directly by a fueledengine. The refrigerant, such as a hydrocarbon or a variant of “Freon”moves through the chiller in a cycle of compression and evaporation,absorbing heat and rejecting heat, thus achieving refrigeration, butrequiring a power source to drive the compressor. Mechanical chillersare distinct from absorption chillers and from turbo-expansion chillers.All three types are used at optimal points in the subject cycle. Themechanical chiller that is integrated with the refrigerant loop ispowered by the same sources (such as wind power), as are the inletcompressor, and the compressors for the refrigerant loop. In addition, asignificant portion of the refrigeration load of the mechanical chilleris reduced by sending it a stream of cold refrigerant from theabsorption chiller, mentioned above, which is driven by recovered heatof compression. The refrigerant air stream used in the refrigerationloop is preferably air, as described in more detail herein, but otherrefrigerants known in the art may also be used. The refrigerant loop air540 travels around subsystem 24 without any blending with the air insubsystem 22, but cooling the air in subsystem 22 by removing heat. Anillustration of one arrangement of refrigerant loop air compressors andrefrigerant loop air expanders can be found on FIG. 1, subsystem 24, asitems 220, 230, and 240, representing the compressors, and items 300 and310, representing the cryogenic expanders. Other configurations may beselected and are covered by embodiments of the present invention.

The mechanical chiller 30 is fluidly connected to thecompressor-expander array, and also fluidly connected to the absorptionchiller, which, by sending a cool stream of refrigerant to themechanical chiller, helps condense the refrigerant within the mechanicalchiller. Thus, the totality of refrigeration applied to the liquefactionof the inflowing compressed air stream is provided by three types ofrefrigerators—compression and expansion, mechanical chilling, andammonia absorption chilling—in an optimal array where each refrigeratoris working within its most efficient range and each reinforces andaugments the cooling work performed by the other. The refrigerant airstream may be directed to and from the main heat exchanger to theindependent refrigeration assembly, which preferably is a closed loopsystem. Thus the refrigerant air stream constitutes a refrigerant airstream in a loop that undergoes refrigeration in several steps byseveral devices, cooling the refrigerant air as it travels through itsloop to temperatures cold enough to liquefy the inflowing compressed,dried, CO₂-free air, with which the refrigerant air is heat exchanged inthe main heat exchanger.

The refrigeration system 24 uses dry air as the working fluid, movingthrough a series of compression, expansion and heat exchange steps in acontinuous loop (the “refrigerant loop process”), independently of theair stream that is compressed, liquefied and sent to storage. The twoair streams never mix, but undergo heat exchange only. Other fluidrefrigerants may be used in lieu of air if desired. The mechanicalchiller 30 may be powered by the same energy input as thecompressor/expansion array, and augmented by the cold refrigerant stream66 from absorption chiller 8. The inclusion of mechanical chiller 30helps increase the efficiency of the independent refrigeration systembut with a modest increase in complexity and capital costs. Theindependent refrigeration system 24 comprises a plurality of compressors220, 230, 240 to compress the refrigerant air stream 540 and a pluralityof expanders, shown here as first and second refrigerant loop aircryogenic expanders 300, 310 to cool the refrigerant air stream. Theplurality of compressors preferably includes a main multi-stagecompressor 220 (preferably four-stage) and first and second boostercompressors 230, 240 (or booster stages). The plurality of expanders mayinclude two expander stages. The compressors and expanders preferablyare all on the same shaft 3, powered by a wind-driven generator/motor600 (or other power source). Other configurations that separate thecompressor stages and/or the expander stages onto multiple shafts withvarious power transmission systems are also feasible. The configurationshown is just one possible arrangement and was selected for illustrativepurposes. Other configurations are contemplated by embodiments of theinvention, and those of skill in the art would be able to employ variousconfigurations.

The refrigerant loop air stream 540 exits the main cryogenic heatexchanger 100 and flows back to the independent refrigeration assembly24, where it is compressed by the plurality of compressors 220, 230, 240and the heat of compression is recovered by the energy flow assembly andsent to power absorption chiller 8. The inflow refrigerant loop airstream 540 sent to the main four-stage compressor 220 is approximately40° F. and about 85 psia, having given up its “refrigeration content”,in the main heat exchanger 100, to the substantially liquefied air 530that is being liquefied for storage. FIG. 1 shows third inter-cooler 720that recovers the heat of compression from multi-stage compressor 220.In reality that third inter-cooler 720 is a group of inter-coolers andan after-cooler, arranged after each stage of compression, but shown inFIG. 1 as a single unit for the sake of clarity. The stream iscompressed to approximately 700 psia, inter- and after-cooled (asdescribed above), and sent to a booster compressor 230, where it iscompressed to a first pressure of approximately 840 psia, and therefrigerant air stream 540 exits the booster compressor at thispressure. The heat of compression is recovered by heat transfer (viaheat exchanger) from the inter- or after-cooler and transferred to anappropriate place in the cycle, such as to the absorption chiller and toa lesser extent to the flash air stream that regenerates the mole sieve.Then refrigerant air stream 540 is after-cooled in a fourth inter-cooler730 and sent to a second booster 240, where it is compressed to a secondpressure and exits at approximately 1,150 psia, after-cooled anddirected to the main heat exchanger 100 at approximately 50° F. Notethat the refrigerant air stream 540 is shown on FIG. 1 with several“splits” in its flow stream, but which all re-connect so that stream 540can be seen as a single continuous loop. It should also be noted thatthe refrigerant stream could be compressed in one stage, but with asubstantially reduced efficiency. As discussed elsewhere herein, thevarious inter- and after-coolers shown in FIG. 1 recover the heat ofcompression that is produced by the several compressors. Secondafter-cooler 740, for example, recovers the heat of compression producedby second booster compressor 240.

The stream is split in two, with one stream moving to the mechanicalchiller 30 and the other stream moving to refrigerant loop air cryogenicexpander 300. The portion that travels to the mechanical chiller iscooled to −40° F. and further cooled in heat exchanger 100 to −80° F.,exiting the heat exchanger with a slight pressure drop, and moving on toexpander 310, exiting that expander at approximately −290° F. and atapproximately 88 psia. The other portion of the stream 540 that did nottravel to the mechanical chiller is cooled by the refrigerant loop aircryogenic expander 300. That portion of stream 540 exits refrigerantloop air cryogenic expander 300 at approximately −204° F. and 87 psiaand joins the portion of stream 540 that exits expander 310. The twostreams join in heat exchanger 540, providing the refrigeration neededto substantially liquefy stream 530.

As mentioned above, approximately 15% of the substantially liquefied air530 will “flash” as the liquid plus vapor enters storage tank 16. Thatvapor portion 535 of the substantially liquefied air, or flash stream,is directed from the L-Air storage tank 16 and travels (at approximately70 psia) to the main heat exchanger 100. There, the vapor portion 535acts as one source of refrigeration, the recovered cold being used tofurther cool the dry inflowing or inlet air 520 described above, whichis moving through heat exchanger 100 as stream 530 in substantially theopposite direction from the path of the flash air 540. The inlet air 530also warms the vapor portion 535 of the substantially liquefied air 550.After cold recovery and further heating from recovered heat, the warmedvapor portion 545, which can now be called sweep air, is further heatedby inter-cooler 700 and directed to the molecular sieve assembly 10where it is used as a “sweep gas” to remove the carbon dioxide andmoisture that has been deposited on the molecular sieve assembly 10. Thewarmed sweep air 545 that exits the molecular sieve 10 and may travelthrough a small, generator-loaded hot-gas expander, which is shown onFIG. 1 as items 345 (the generator-loaded hot-gas expander), shaft 3 (arotating shaft that connects the expander to a generator), and 630, thegenerator. That assembly would provide some of the power needed byinstruments and the like, recovering a worthwhile portion of the energyremaining in the hot sweep gas. The now expanded and cooled sweep gasleaves the system by way of air vent 19. That sweep gas merely returnsthe CO₂ and moisture content of the original inlet air 500 to thesurrounding atmosphere. No additional CO₂ or moisture is sent outthrough vent 19.

As discussed throughout, the various compressors generally are notdriven directly by a wind turbine or another intermittent power source,but by motors that receive electric power from wind turbines, from asmall portion of the power output of the system, from a base-load powerplant where the system may be deployed or from the electric grid, orfrom any other power source(s). As is understood by those familiar withpower production systems, generators and motors are essentially thesame, but with one rotating in the opposite direction from the other.For example, FIG. 1 shows a wind turbine driving the independentrefrigeration system generator 600, which in turn provides power bycable 4 to a motor 605, which drives the compressors on shaft 3, shownas independent refrigeration system 24. The independent refrigerationsystem motor 605 may get its power from any other power source, not justthe wind-turbine-driven generator 600 shown above it.

It should be noted that FIG. 1 illustrates an embodiment of the inletair compression, clean up, refrigeration and energy storage systems ofthe present invention. Much of the piping, valves, sensors, insulation,and other “hardware” and software that would be part of an engineereddesign of the same embodiment are not shown because all such aspects arewell understood by gas processing and power production engineers.Similarly, the internal configurations for the absorption chiller, theinter- and after-coolers, the mole sieve, the expanders, compressors,generators and motors are not shown. Power cable connections 4 are shownin several places in FIG. 1, connecting power-producing generators withmotors that drive compressors. Other cables, not shown, would connect toinstruments, electrically operated valves and the like.

Various other arrangements of the inflow/energy release and replacementsystem 20 using the same or similar components can be arranged tooptimize the cost and performance of the system and to create a compact“footprint” at the deployment site. The scale of the system can alsovary, possibly to under 2 MW of firm power output and up to hundreds ofMW of output, where land is available for the required amount of L-Airstorage.

Turning to FIG. 2, an energy release system and method, or energysend-out mode, is shown. FIG. 2 shows energy release system 50 and itssubsystems, but, for the sake of clarity, in a manner that does not showthose elements of the overall system that are dormant during outflow.For example the cryogenic refrigeration loop described above is notshown in FIG. 2, even though it would still be physically connected tothe main heat exchanger 100. The absorption chiller is not shown becauseit is not needed during send-out. Similarly, a cryogenic pump shown inFIG. 2, as part of the outflow process, was not shown in FIG. 1, eventhough it is generally connected to the L-Air storage tank(s) 16 readyfor service.

An embodiment of the invention includes a method of releasing storedenergy, by the release of “outflow” liquid air as described here. Storedliquid air 550 is released from storage apparatus 16, pumped to pressureby cryogenic pump 17, such that the released high-pressure liquid air550 flows in a first general “outward from storage” directionsubstantially opposite to a second general direction in which theindependent loop of air flows, which loop of air acts as a workingfluid, being condensed and liquefied by the main outflow air stream andbeing heated, vaporized by recovered waste heat, as described below, andwhere the vaporized air is expanded in a generator-loaded hot-gasexpander, producing a portion of the power that is sent out during theenergy release mode. In this context the terms “independent loop of air”or “working loop air” is meant to cover the independently circulatingair in subsystem 55, shown on FIG. 2, and noted by reference numbers551, 570, and 575. The term “working” is used here in the same sense asone might use “working fluid”, for example the water-to-steam cyclesthat are common in combined cycle power plants. In this context theworking loop air is liquefied, pumped to pressure, heated by heatexchange, expanded in a generator-loaded expander—hence work isperformed—partially cooled during expansion, then further cooled by heatexchange, then liquefied (condensed), allowing the cycle to begin again.

The released liquid air that leaves the cryogenic liquid air storagevessel is first pumped to pressure, preferably by a cryogenic pump. Thereleased liquid air 550 flows past the counter-flowing working loop air575 such that heat exchange occurs between the two air streams. Thecounter-flowing working loop air 575 (which is the smaller stream) warmsthe released liquid air 550 by heat exchange such that the releasedliquid air is substantially vaporized, and the released liquid air coolsthe loop air 575 by heat exchange such that the “loop air” issubstantially liquefied. As the loop air 575 is liquefied by the largerstream of liquid air, it arrives at a temporary storage or buffer tank160, after which it is pumped to pressure, warmed in heat exchanger 150by hot exhaust gas streams 5 which delivers exhaust heat from agenerator-loaded hot-gas expander 330 (more fully described below) andexpanded in a generator-loaded hot-gas expander 340 shown as 621(generator) and 340 (expander which are fluidly connected on shaft 3,and where the generator is an air bearing type where air stream 555supports the rotating generator within housing 11 and takes away theheat of friction, thus helping to warm air stream 555 at points B andB′, as shown in FIG. 2, prior to the air arriving to heat exchanger 102.Its remaining heat is used to pre-warm the larger, high-pressurevaporized formerly-liquid air stream 555 that is on its way tocombustion chamber 2, where that outbound air combusts with a fuel 12(such as natural gas delivered by pipeline 9), after which the hot,high-pressure product of combustion 5 is sent through one or morehot-gas expanders that are generator-loaded, converting the energycontent of the previously liquid air into electricity, and over severalhours, emptying the liquid air storage tank 16 so that it is again readyto store energy, as liquid air. The generator 620 is also of an airbearing design, such that air stream 555 is diverted to generator 620,as indicated by points A and A′, allowing the cold air to be warmed bythe heat of friction produced by the rotating generator 620, and thuspre-warming stream 555 on its way to heat exchanger 102.

Thus, the preferred embodiment produces electric power in two “modes”;as a consequence of the expansion of the heated and vaporizedhigh-pressure “loop air” (which is never sent to a combustion chamber),and as a consequence of the larger stream of outgoing air that helpscombust a fuel, producing a large stream of hot gas which is expanded toproduce the major portion of the electricity output.

Also, FIG. 2 shows some of the same elements shown in FIG. 1 but inslightly different positions. For example, in FIG. 1, the main heatexchanger is shown in close proximity to L-Air storage tank 16, whereasin FIG. 2 cryogenic heat exchanger 130 is shown between tank 16 and heatexchanger 102.

FIG. 2 shows the cold L-Air 550 and cold pressurized air 555 moving “up”from storage, with warm counter-flowing expanded air 575 (orcounter-flowing loop air) that travels in a closed loop 55 acting as acold recovery medium in cryogenic heat exchanger 130. This is animportant feature of this preferred embodiment because the refrigerationcontent of the stored L-Air is recovered to “condense” (liquefy) astream of air that is subsequently heated and then expanded to produceadditional power, as outlined below.

The stored L-Air 550 is released from storage and leaves the storagetank(s) 16 at −283° F. and approximately 70 psia by way of a cryogenicpump 17 that pressurizes the liquid by pumping it to a pressure ofapproximately 590 psia. It should be noted that other pressures wouldalso work and would depend on the selected hot-gas expanders and thedesign pressures under which the expanders operate. That pumpingrequires very little energy (approximately 0.1 MW) because a liquid is(virtually) incompressible and will achieve that pressure with verylittle energy input. Cryogenic pump 17 is driven by pump motor 630 whichreceives a small portion of the total power output of the system bycable 4. It should be noted that the pumped-to-pressure effect of thecryogenic pump 17 yields “compressed” air, once the air is vaporized,and that the terms “pumped to pressure” and “compressed” cover the samestate of “high-pressure” where the first term applies to the liquidstate of the air, and the second term applies to the vaporized state.

The pumping of the L-Air 550 to approximately 590 psia raises itstemperature slightly, to about −280° F. The high-pressure, cryogenicL-Air 550 then travels through cryogenic heat exchanger 130, liquefyingthe counter-flowing “loop” air that is the working fluid that isexpanded in generator-loaded hot-gas expander 340, which is loaded bygenerator 621, yielding approximately 23% of the system's total poweroutput, or approximately 28% of the power output of the main generator620. Thus, liquid air stream 550 is vaporized by “loop” air stream 575,which in turn is liquefied by the cold content of 550, but not at thesame flow rate. That cold recovery exchange occurs at a rate where the“loop” airflow is approximately 84% of the flow rate of the mainoutbound stream 555. The cold pressurized air 555 (formerly L-Air) isfurther warmed in heat exchanger 102 by the warm “loop” air 575 thatleaves generator-loaded hot-gas expander 340 and by the larger stream 5that leaves the main hot-gas expander assembly that drives generator620.

Continuing with FIG. 2, the stream of outflow air 555 leaves heatexchanger 102 at approximately 900° F. and approximately 588 psia,arriving at combustion chamber 2 where it combusts the fuel stream 12that has been boosted to the same pressure by compressor 260, which isdriven by motor 630, powered by electricity delivered by “wire” 4, andthe fuel stream having been delivered to compressor 260 by fuel line 9.

The combustion chamber 2 is housed in a heat exchanger housing 111 thatallows for the re-warming of return exhaust streams as shown in FIG. 2.For example, after the hot, high-pressure combustion gas 5 leavescombustion chamber 2 and is expanded in first generator-loaded hotgas-expander 320, it is returned for warming in heat exchanger 111, andthen sent on for further expansion in second generator-loaded hotgas-expander 330. This is known in the industry as a “two stageexpansion with reheat” and serves to increase the efficiency of the hotgas expansion (and power generation) cycle. Other configurations forexpanding the hot gas that is the product of combustion may be used,some yielding lower capital costs and lower efficiencies and otherscosting more and yielding slightly higher efficiencies. Theconfiguration shown in FIG. 2 is meant as an illustration of onearrangement but is not meant to exclude other arrangements.

Stream 5, leaving generator-loaded hot-gas expander 330, is shown“split” by valve 400. A larger portion is sent on to heat exchanger 102,as described above, and then on toward flue 18. A smaller portion issent to heat exchanger 150 where it helps to vaporize and heat theliquid air 551 that leaves a buffer tank 160 and which is first pumpedto pressure by a cryogenic pump 17, which is driven by motor 640. Itshould be noted that the use of reference numbers, 600, 605, 610, 630,640, etc. for the various motors in the system does not suggest anythingabout the size and capacity of each referenced motor. The specific poweroutput of each motor will be determined by the engineering decisionsthat are applied to the system when each deployment is designed.Continuing with the cold recovery and power generation loop 55, the hot,high-pressure air 570 leaves heat exchanger 150 at approximately 900° F.and 1,200 psia and is expanded in third generator-loaded hot-gasexpander 340, exiting at approximately 425° F. and 200 psia as stream575. That heat content helps warm the main outflow air stream in heatexchanger 102, as described above.

FIG. 2 shows several “breaks” in the gas streams as a simple way toindicate cold and heat recovery steps. For example the main outflowstream 555 is shown “broken” at A to A′, indicating that a portion ofstream 555 is first sent to main generator 620 as bearing air that helpsfloat the rotating generator 620 in its housing 11. In this manner,stream 555 picks up the heat of friction from the rotating generator,cooling the generator, and pre-warming stream 555 before it enters heatexchanger 102. Thus, points A to A′ located between heat exchangers 130and 102 are the same A to A′ points shown near generator 620. Similarly,a portion of stream 555, represented by points B to B′ between heatexchangers 130 and 150 serve the same “air bearing” heat recoveryfunction in secondary generator 621 and correspond to stream 555 shownbetween points B and B′ near generator 621. Another “stream break” isindicated by the set of points on FIG. 2 marked C, showing how heat isrecovered in heat exchanger 150 from the portion of the hot exhauststream that travels through heat exchanger 150, warming stream 551. Thecooled exhaust gas stream 6 that exits heat exchanger 150 is shownending at point C which corresponds to point C above D′ near flue 18.Thus, point C near heat exchanger 150 is the same point as point C shownnear flue 18. Similarly the set of points D and D′ represent the heatrecovery of the main exhaust stream 5 giving up its remaining heat(after it leaves heat exchanger 102) and also warming stream 551 in heatexchanger 150. Similarly, the warm loop air stream 575 that leaves heatexchanger 102 at approximately 120° F. is “broken” at points E to E′,indicating that the remaining heat content of stream 575 is used to warmthe moisture 801, which is recovered in moisture separator 800 in warmheat exchanger 140, so that the pumped-to-pressure moisture 803 can besent to generator-loaded hot-gas expander 330 as a high-pressure watervapor stream, thus increasing the mass flow through the expander, andimproving its power output.

Power cable connections 4 are shown in several places in FIG. 2. Eachsuch cable may be differently sized from any other cable, reflecting therequired amount of power it needs to carry. Other cables, not shown,would connect to instruments, electrically operated valves and the like.

Shop fabricated L-Air storage tanks are readily available. Horizontaltanks can be deployed in “sculpted earth” containment areas where amodest depression in the local grade level 25 is created to contain thetanks behind a modest berm that is assembled from the excavatedmaterial. Such a configuration will yield a very-low profile for thestorage tanks. Three 75,000-gallon shop fabricated L-Air storage tanksis preferred for the model outlined herein, but fewer may be useddepending on the circumstances, and field-erected tanks of the same orlarger capacity may also be used. A fourth or fifth tank wouldsubstantially increase the storage and outflow options, allowing forextra input capacity during weekends and on windy nights and allowingfor “excess air send-out” during high-demand periods, as discussedabove. That extra degree of flexibility is achieved by the relativelylow-cost and low-tech effort of adding one or two L-Air storage tanks tothe basic three that are required to keep the inflow and out-flow modesin balance.

In addition to low-pressure (under 100 psia) cryogenic storage tanksthat would contain liquid air, the present invention also contemplatesthe storage of cold-compressed-air (CC-Air) in cryogenic pressurevessels. CC-Air can be defined as a vapor (non liquid) form of air thatis very cold (for example, colder than −200° F.) and at a significantpressure (for example, more than 500 psia), such that the density of theCC-Air is more than 32 pounds per cubic feet (for example, achieving 70%of the density of L-Air). Such CC-Air can be pumped to a higher pressurewith very little additional energy input, much like L-Air, and can bestored in a relatively efficient storage vessel because, atapproximately 70% the density of L-Air, it is significantly denser thancompressed air, but having the benefit of requiring some 30% less energyinput to produce. Thus, the present invention also includes theproduction, storage and release of CC-Air. That option will likely bemost viable in smaller embodiments of the invention, say, under 10 MW ofstored energy output, where the size of the storage vessel(s) is not ascritical as the energy input to produce the stored air. Indeed, thepresent invention includes a wide range of dense cryogenic air storageoptions, from the near-liquid CC-Air option at 500 psia and higher, tothe L-Air option at under 100 psia and any such dense-phase cryogenicair conditions, at any appropriate temperature and pressure, where thecombination of temperatures and pressures yield air that has a densityin excess of approximately 25 pounds per cubic feet.

FIG. 2 shows fuel pipeline 9 delivering a fuel stream 12, which would benatural gas in some cases, to fuel booster compressor 260 that bringsthe pressure of the NG to the design pressure of generator-loadedhot-gas expanders 320 and 330. Other fuel delivery methods would workequally well. For example, as an alternative to pipeline-delivered NG,embodiments of the invention can use landfill gas, anaerobic digestergas, or coal bed methane as a fuel source, or NG from a “stranded well”or “associated gas” that is found with oil wells. In some instances, thefuel stream would need no booster compression because, for example atsome stranded gas wells, the pressure of the gas stream would be as highor higher than the design pressure for the generator-loaded hot-gasexpanders 320 and 330.

FIG. 2 shows a fuel booster compressor 260 for the natural gas (NG) fuelstream 12, raising the pressure of that stream from, e.g., 60 psia to588 psia, the same as the assumed pressure of the compressed air thatarrives at combustion chamber 2. That booster compressor uses verylittle energy (less than 0.3 MW) relative to the total power output ofthe energy release stage of the system. It will use even less energy ifthe fuel gas arrives at the site at a higher pressure, such as from ahigh-pressure regional natural gas transmission line or from certainstranded gas fields. Other fuels can be substituted for the NG at theappropriate rate (relative to the compressed air flow), yielding similarpower output results. If wind power were also available during the poweroutput cycle outlined above, its energy would be added directly to theoutput of the power plant, rather than converted to L-Air. The exhaustgas leaving the combustion chamber, or combustion gas, is about 2,000°F., but this high temperature is achieved with less fuel than in othercycles because the inlet air was pre-warmed to about 900° F. Theapproximately 2,000° F., about −8 psia combustion gas is expanded in atwo-stage generator-loaded hot-gas expander 320, 330, first toapproximately 98 psia and then down to about 16 psia. The somewhatcooled outflow from the first stage of expansion 320 is re-heated toabout 2,000° F. at the combustion chamber, and sent to the second stage330 (at approximately 96 psia), leaving the second stage atapproximately 1,141° F. and about 16 psia. As discussed above, theexhaust stream 5 that leaves generator-loaded hot-gas expander 330 issplit in two by a valve. Each portion of the split stream is used toheat other streams, as discussed above, in heat exchangers 102 and 150.The two streams rejoin as stream 6 and arrive at moisture separator 800,where the moisture content of the cooled exhaust gas 6 is separated andsent on partially toward drain 802 and in part through a pump 13 andwarm heat exchanger 140 and then to generator-loaded hot-gas expander330. The moisture content of cooled exhaust stream 6 can be separatedout because the stream has cooled enough to allow the moisture tocondense. However, not all of the recovered moisture can be used bygenerator-loaded hot-gas expander 330, so some of the recovered moistureis sent to drain 802. Pump 13 pressurizes that moisture, with verylittle energy input (because liquids are virtually incompressible andthus reach a desired pressure with very little energy input). When thathigh-pressure 801 stream is heated in 140 it leaves as mostly vapor 803,thus providing a low-cost way to increase the mass of the gas streamthat is being expanded in 330. The purpose of stream 803 is to increasethe hot-mass-flow through generator-loaded hot-gas expander 330, thusimproving the power output of generator 620.

For applications of the VPS Cycle for wind power storage, eachdeployment of an embodiment of the invention will likely be based on asite's “wind history”, and projected “capacity factor”, accounting forday/night and seasonal patterns, which would be projected forward, andcompared to peak electric demand that would also account for day/nightand seasonal patterns. The total amount of L-Air storage chosen for eachsystem deployment will balance the need for certainty andwind-reliability against the cost of storage (tanks, valves, andpiping), within the limitations of the land area available for thestorage system.

Thus, it is seen that energy storage and release systems and methods areprovided. It should be understood that any of the foregoingconfigurations and specialized components may be interchangeably usedwith any of the systems of the preceding embodiments. Although preferredillustrative embodiments of the present invention are describedhereinabove, it will be evident to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. It is intended in the appended claims to cover all suchchanges and modifications that fall within the true spirit and scope ofthe invention.

1. A liquid air production system comprising: one or more inlet aircompressors; a molecular sieve assembly fluidly connected to a firstinlet air compressor; a vertical cold flue assembly fluidly connected tothe molecular sieve assembly and to a second inlet air compressor, thevertical cold flue assembly having an air inlet at or near its top intowhich inlet air is directed and an exit at or near its bottom; one ormore inlet air heat exchangers including a main heat exchanger fluidlyconnected to at least one of the plurality of inlet air compressors; astorage apparatus fluidly connected to the main heat exchanger; anabsorption chiller using a working fluid, the absorption chiller beingfluidly connected to the cold flue assembly; and a mechanical chillercontaining refrigerant fluid, the mechanical chiller being fluidlyconnected to the absorption chiller; and a refrigerant loop air assemblyfluidly connected to the mechanical chiller.
 2. The system of claim 1wherein the refrigerant loop air assembly comprises: one or morerefrigerant loop air compressors, at least one of the plurality ofrefrigerant loop air compressors being fluidly connected to the mainheat exchanger; one or more refrigerant loop air cryogenic expanders;wherein the mechanical chiller is fluidly connected to at least onerefrigerant loop air compressor, at least one refrigerant loop aircryogenic expander, the absorption chiller, and to the main heatexchanger; and wherein refrigerant loop air flows from the refrigerantloop assembly to the main heat exchanger to cool the inlet air.
 3. Thesystem of claim 2 wherein the refrigerant loop air is compressed by theone or more refrigerant loop air compressors and the heat of compressionis recovered by at least the absorption chiller.
 4. The system of claim3 further comprising at least one valve, wherein the refrigerant loopair is split by the at least one valve such that a first portion isdirected to the mechanical chiller and a second portion is directed toat least one refrigerant loop air cryogenic expander; the refrigerantloop air is cooled by the mechanical chiller and by the one or morerefrigerant loop air cryogenic expanders and is directed to the mainheat exchanger; and the refrigerant fluid within the mechanical chilleris condensed by cold working fluid sent to the mechanical chiller fromthe absorption chiller.
 5. The system of claim 1 wherein recovered coldfrom a vapor portion of the substantially liquefied air further coolsthe inlet air in the main heat exchanger; the vapor portion of thesubstantially liquefied air is warmed by heat from the inlet air andrecovered heat of compression; and the warmed vapor portion of thesubstantially liquefied air is directed to the molecular sieve assemblysuch that the vapor portion of the substantially liquefied air removescarbon dioxide and moisture from the molecular sieve assembly.